Recently, great attention has been drawn to renewable energy sources. Clean natural energy such as wind energy has gained favor as lower cost and more environmentally friendly alternatives to the traditional energy source of fossil fuel, which has disadvantages such as fuel shortage and air pollution.
With this growing interest, considerable efforts have been made to develop wind turbines that are reliable and efficient for receiving and converting wind energy into electric power. Generally, a wind turbine includes a rotor and a plurality of blades engaged with the rotor. The rotor may be coupled with one or more generators. The plurality of blades receives wind energy and transforms it into a rotational torque or force that drives the rotor, which in turn drives the one or more generators to generate electricity.
Depending on the layout of the rotor and blades, wind turbines are classified into horizontal axis wind turbines and vertical axis wind turbines. In a horizontal axis wind turbine, the blades are adapted such that when wind flows towards the blades, a propelling force is generated and causes the blades to rotate around a horizontal axis. The horizontal axis wind turbine usually requires the blades be very long and a very tall mounting tower support them, which may pose disadvantages in cost for transportation, installation and maintenance.
In a vertical axis wind turbine, the blades are adapted such that when wind flows towards the blades, a propelling force is generated and causes the blades to rotate around a vertical axis. A vertical axis wind turbines has little or no need for a tower on which the turbine is mounted. One predominant vertical axis wind turbine is commonly referred to as a Savonius wind turbine. The rotor blades or vanes are traditionally semi-cylindrical shaped and coupled to a central shaft. The principle of operation of Savonius wind turbine machine is based on the difference in the drag forces of semi-circular vanes extending horizontally on a rotor, where one semi-circular vane is oriented so as to be concave while the counterpart vane is oriented to be convex. When placed in an air stream, the drag difference between the concave vane and the convex vane causes the rotor to rotate. Advantages of this type of machine are that it is self-starting, does not require aiming into an incident wind direction, is simple to design, and has low construction cost. However, it has relatively low efficiency.
Therefore, it is desirable to develop a wind turbine that addresses the above mentioned drawbacks.